Flood scheme stock bridge complete soon
2 May 2016, 9:55 AM
A 54-metre long stock bridge under construction as part of work designed to better protect Kaitaia and the wider Awanui catchment from the effects of flooding should be completed within weeks.
Monty Knight, who represents the Northland Regional Council’s Te Hiku constituency, says the $250,000 bridge is being built on the boundary of two farms about 2.5 kilometres downstream from the recently modified Whangatane Spillway weir.
The council spent about $150,000 modifying the weir over summer, which will now allow floodwaters to enter the spillway from the Awanui River much earlier during floods.
Councillor Knight says the changes reduce the flood risk to urban Kaitaia by lowering peak flood level at the spillway intake and upstream along the Awanui River through Kaitaia.
“It should also reduce the ‘backwater effect’ at bridges across the Awanui River through Kaitaia itself, as well as help floodwaters drain more quickly from Lake Tangonge.”
He says floodgates on the river downstream of Kaitaia will be able to be open for longer before floods peak, as more water will flow down the spillway during a flood’s early stages. “It will also allow floodgates along the lower Awanui River to open sooner once a flood’s peak has passed.”
However, Councillor Knight says while potentially thousands of people will benefit from these improvements, they will come at the cost of more frequent flooding of the spillway, which runs through at least half a dozen downstream farms.
“The scheme could not have been improved to the extent it has without the support and understanding of these farmers and I’d like to express the community’s heartfelt thanks to them.”
Councillor Knight says two of the most affected properties are adjoining, but separate farms, one owned by Malcolm Matthews and the other by Roger Matthews. Both properties straddle the spillway and their owners faced the prospect of regularly not being able to move from one side to the other during the wetter months.
The council’s solution is the shared 54-metre stock bridge that will service both properties, spanning the floodwaters expected to be delivered by the upstream scheme modifications.
Steve Bowling Contracting Ltd started work on the bridge in late March and the project is scheduled for completion in a few weeks, well ahead of winter rain.
The Whangatane weir and spillway are on the north-east bank of the Awanui River, about 260 metres upstream of State Highway One’s Waikuruki Bridge. The spillway flows for about 14km and discharges directly to the Pairatahi Stream, then into Rangaunu Harbour.
Water that does not flow over the intake weir travels for about 24km along the lower Awanui River instead, before eventually discharging to the harbour at Unahi.
The current works are the latest in a series of scheme improvements the regional council and Awanui River Management Liaison Committee have approved on behalf of the local community in recent years.